Chapter 5.2 Calorimetry
a technique used to measure the amount of heat involved in a chemical or physical process
used to measure amounts of heat transferred to or from a substance
substance undergoing the chemical or physical change
the other components of the measurement apparatus
that serve to either provide or absorb heat from the system
device used to measure the amount of heat involved in a chemical or physical process
How do readings of a calorimeter help calculate the amount of heat change?
the heat is either raised or decreased in a calorimeter
the temp change (ΔT) along w/ specif heat (c) and mass (m) of the soln
can be used to calculate the amount of heat involved in either type
of process (exo or endo)
- well-insulated to prevent the transfer of heat w/ outside enviornment
- can be made w/ 2 polystyrene coffee cups (less accurate b/c more heat exchange w/ outside environment - usu include a stirrer
- more expensive ones used for industry and research= more accurate
Under ideal circumstances, what is the net heat change of two substances?
qsubstanceM + qsubstanceW = 0
What does the negative sign indicate in the relationship btwn substances?
it merely shows that they are opposite in direction of heat flow (gain or loss)
What determines the arithmetic sign of the q (heat) value?
by whether the matter in question gains or loses heat
in ex: qmetal was negative b/c it lost heat= -qmetal
When is it not okay to neglect very small amounts of heat absorbed by the calorimeter?
not for highly accurate measures
What does the calorimeter do when working with chemical reactions?
minimizes energy exchange w/ the environment
Explain the chemical reaction heat formula
heat produced/consumed in the reaction "system" [qreaction]
plus the heat absorbed/lost by solution "surroundings" [qsolution]
must add up to zero
qreaction + qsolution= 0
Chemical heat reaction formula
What does it mean?
This means that the amount of heat produced/consumed = the amount of heat absorbed/lost by the solution
qreaction = -qsolution
What happens when amount of heat of calorimeter is too large to neglect or if more accurate results are needed?
must take into account heat absorbed both by the solution and calorimeter
used to measure the energy produced by reactions that yield large amounts of heat and gaseous products, such as combustion rxns
it operates at constant volume